CHAPTER 2Overview of Cellular Physiology in Medical Physiology 41
FIGURE 2–10 Rough endoplasmic reticulum and protein translation. Messenger RNA and ribosomes meet up in the cytosol for transla-
tion. Proteins that have appropriate signal peptides begin translation, then associate with the endoplasmic reticulum (ER) to complete translation.
The association of ribosomes is what gives the ER its “rough” appearance. (Reproduced with permission from Widmaier EP, Raff H, Strang KT: Vander’s Human
Physiology: The Mechanisms of Body Function, 11th ed. McGraw-Hill, 2008.)
Cytoplasm
Extracellular fluid
mRNA from Gene A mRNA from Gene B
Free ribosome
Signal sequence
Rough
endoplasmic
reticulum
Growing
polypeptide
chain
Carbohydrate
group
Cleaved signal
sequences
Vesicle
Golgi apparatus
Secretory vesicle
Plasma membrane
Exocytosis
Digestive
protein
from
Gene B
Lysosome
Secreted protein
from Gene A